TAKE HOME MESSAGES

• In high yielding environments in northern Illinois, 2-year data from ten “grain” hybrids averaged 8.4 bushels of corn (15% moisture) per ton of 35% DM silage.
• Silage quality factors were not highly correlated with grain yield or silage yield.
• Grain yield was not a good predictor of silage yield.

INTRODUCTION

Corn silage is an important ingredient in dairy and beef rations. Acres of Illinois corn harvested for silage in 2002 were 130,000 and the yield was 16 tons per acre (Illinois Agricultural Statistics, 2003 Annual Summary). Determining a fair price for corn silage is difficult due to the many variable factors involved with this commodity. One approach has been to price corn silage based on grain value. In the past, a ton of corn silage standing in the field has been valued at 6.5 to 7 times the market price of a bushel of corn. If in storage, the value was 10 times the market price of a bushel.

MATERIALS AND METHODS

A study was initiated in 2002 at the Northern Illinois Agronomy Research Center, Shabbona ( DeKalb County) to determine the relationship between grain yield and silage yield in corn. Results from 2002 and 2003 are reported here. Ten “grain” hybrids, shown in Table 1, ranging from 103- to 112-day maturity were planted in 4, 30-inch rows and thinned to 32,000 plants per acre. Planting date varied from April 29 (2003) to May 8 (2002). Soil type was Flanagan silt loam. One-half of the plot was harvested for silage yield and the other half harvested later for grain yield. Silage harvest dates were September 13 (2002) and September 18 (2003). Plants for silage yield were hand-harvested, leaving a 6-inch stubble, and processed using a “chipper shredder” to simulate a forage chopper. A “grab” sample was taken for laboratory analysis. Grain yield was determined from combining.

RESULTS AND DISCUSSION

Grain and silage yield results averaged for the 10 hybrids and the two years are shown in Table 2. Silage quality results averaged for the 10 hybrids and the two years are summarized in Table 3. The correlation of selected silage quality factors to yield, averaged over the two years, is shown in Table 4. Correlation is the tendency for two variables to be related in a certain manner. For example, a perfect positive correlation is +1.0, a high positive correlation is +0.80, a medium negative correlation is -0.50, a zero correlation is 0, etc. As shown in Table 4, silage quality factors were not correlated very well with silage yield or grain yield. Silage moisture was not highly correlated (-0.558) to kernel milkline. Based on the first two years of a 3-year study, we were not able to predict the grain yield based on silage yield very accurately. The correlation of grain yield to silage yield was 0.403. The correlation of bushels of grain per ton to silage yield was –0.761

ACKNOWLEDGEMENT

Financial and in-kind support: Northwestern Illinois Forage & Grassland Council and Agri-King Inc., Fulton, IL

Table 1. Hybrids grown in the study by year.

Table 2. Grain and silage yield results.

Table 3. Silage quality results.

Table 4. Correlation of silage quality factors to yield.